By joining the growing faction of N.B.A. players who choose to wear a mouth guard in games, a player is forced to confront a certain small issue: Where do you keep the thing when you’re on the bench?

Mason Plumlee of the Nets tucks his mouthpiece inside one of his socks, which he acknowledged is “not the most sanitary place in the world.” Rajon Rondo of the Dallas Mavericks has been observed spitting his straight down through the collar of his jersey — though where it lands, exactly, has remained something of a mystery. Cole Aldrich of the Knicks often takes the curved, wet plastic and hooks it around one of his ears.

“Some guys put it in their spandex, and some guys put it in their sock, but I think that’s gross,” said Aldrich, who looked surprised when it was suggested that some might consider his method comparably disgusting. “I shampoo my hair every day, so I think my head is pretty clean.”

Such concerns barely existed a generation ago, when the mention of mouth guards mostly evoked images of football players. Players who used them in the N.B.A. were few and far between. But during the past decade, the mouth guards have undergone sleek design improvements, and research during that time has increasingly shown that the benefits of wearing one may go beyond simply shielding one’s teeth.

The sight of LeBron James nervously chewing on his mouth guard has become a quintessential image of the league’s national television broadcasts. Blake Griffin has soared for dunks with a mouthpiece casually dangling against his cheek. Last season, Stephen Curry became a spokesman for a line of flavored mouth guards; a few months later, he received a technical foul in a game after flinging his mouth guard across the court in frustration.

Mouth guards worn by N.B.A. players, such as the Knicks' Tim Hardaway Jr., must be one solid color and cannot bear any designs other than a team logo.CreditAlex Goodlett for The New York Times

“I see everyone playing around with them during games, and I’m starting to feel left out,” said Brook Lopez of the Nets, who has never worn one.

David Stern noticed the developing trend during his time as league commissioner, from 1984 to 2014. He wrote in an email that it made sense that players might want to protect themselves “in the event of ‘inadvertent’ elbows.”

Self-preservation can be a strong impulse. Dwyane Wade, who entered the N.B.A. in 2003, began experimenting with a mouth guard in the 2013 playoffs, during a particularly physical series against the Chicago Bulls.

Jason Smith of the Knicks said that he usually does not wear a mouth guard, but that he has one ready just in case he is guarding someone known to be particularly aggressive. Smith’s teammate Amar’e Stoudemire said that he appreciated the additional safety, but that he stopped wearing mouth guards as frequently because he found it difficult to yell and communicate on defense.

Alan Anderson of the Nets last month. Credit Adam Hunger for The New York Times

Plumlee has refused to play basketball, in a game or practice, without one since a hit to his mouth before his junior year at Duke forced him to undergo four root canals and then wear braces.

“I had braces for a long time as a kid,” he said, shaking his head, “and then, imagine, here I was, a junior in college with braces again.”

This season, Plumlee began working with a new company called GuardLab, whose marketing efforts seem to reflect the changing concept of mouth guards. In an interview, Flint Reilly, one of the company’s founders, noted the equipment’s usefulness in safeguarding against concussions and reducing muscle tension throughout the body.

Stephen Curry of the Warriors in December.CreditJeff Chiu/Associated Press

That is the same reason that Martell Webster of the Washington Wizards has, for the past few seasons, worn a thin, clear retainer that does little more than create separation between his top and bottom rows of teeth and encourage an optimal jaw alignment.

“Everything is connected, so relaxing your jaw has an overall relaxing effect on your muscles,” Webster said. “Your body is looser, and in sports, especially basketball, you want to be as loose as you can.”

Stern said the league never had major aesthetic concerns about the increased popularity of mouth guards, but he heard complaints.

“Some players were less elegant than others in the way they allowed them to dangle from their mouths when at rest,” Stern wrote in the email.

The Nets’ Mason Plumlee, left, tucks his mouthpiece inside one of his socks, which he acknowledged was “not the most sanitary place in the world.”CreditAdam Hunger for The New York Times

The league regulates mouth guards largely the same way it does other supplementary equipment, like compression sleeves or rubber wristbands. They must be one solid color — white, black, a primary team color or clear — and cannot bear any logos or designs other than a team logo. They must take the form of a player’s mouth.

Entering the 2012 postseason, James put the Roman numerals XVI on his mouth guard, indicating the number of postseason victories needed to win a trophy. Curry last season wore one with his surname stretched across the front. Such designs would seem to violate current uniform regulations.

With mouth guard in hand, Cleveland’s LeBron James questioned a call in a game at Detroit.CreditPaul Sancya/Associated Press

Clear contraventions involving mouth guards have become more common. Two seasons ago, Amir Johnson of the Toronto Raptors was suspended for one game after throwing his mouthpiece at the referee David Jones on the court. Earlier this season, Enes Kanter of the Utah Jazz was fined $25,000 after throwing his mouth guard into the stands while arguing a call.

The fan who picked it up held it aloft, proudly, as if he had caught a home run ball at a baseball game.